|  | 4.3 | Layer 1 Design
| 4.3.5 | Elements of a logical topology diagram

As shown in Figure , the logical diagram is the network topology model without all the detail of the exact installation path of the cabling. It is the basic road map of the LAN. Elements of the logical diagram include: The exact locations of the MDF and IDF wiring closets. The type and quantity of cabling used to interconnect the IDFs with the MDF, along with how many spare cables are available for increasing the bandwidth between the wiring closets. For example, if the vertical cabling between IDF 1 and the MDF is running at 80% utilization, you can use two additional pairs to double the capacity Detailed documentation of all cable runs, as shown in Figure , the identification numbers, and which port on the HCC or VCC the run is terminated on. For example, say Room 203 has lost connectivity to the network. By examining the cutsheet, you can see that Room 203 is running off cable run 203-1, which is terminated on HCC 1 port 13. You can now test that run by using a cable tester to determine whether the problem is a Layer 1 failure. If it is, you can simply use one of the other two runs to get the connectivity back and then troubleshoot run 203-1.
| Threaded Case Study
Washington Project: Layer 2 Design Goals
The following are Layer 2 LAN topology design goals for the sites of the Washington School District network:

- You should install LAN switching devices that use micro-segmentation in order to reduce the collision domain size.
- You should create VLANs and unique broadcast domains based on user workgroups.